Rock bit dullness indicator



w. J. BIELSTEIN 3,363,702

ROCK BIT DULLNE'SS INDICATOR Jan. 16, 1968 Filed July 27, 1966 INVENTORYWALTER J. BIELSTEHI,

ATTORNEY.

United States Patent 3,363,7tl2 ROCK BIT DULLNESS INDICATOR Walter J.Bielstein, Houston, Tex, assignor to Esso Production Research CompanyFiled July 27, 1966, Ser. No. 558,333 5 Claims. (Cl. 175---39) Thepresent invention concerns drill bit apparatus for use in drillingboreholes in the earth. More particularly, the invention concerns aroller cone-type drill bit which, when Worn to the extent that furtheruse of the bit would result in inefficient drilling operations, willgive an indication of such wear at the surface of the earth.

In rotary drilling, a commonly used method in drilling boreholes, adrill bit attached to the lower end of a string of drill pipe issuspended from the surface of the earth. During drilling operations, adrilling fluid under high pressure is forced downwardly through thedrill string, through the drill bit and back to the surface through theannulus between the drill pipe and the wall of the borehole. The drillbit is rotated by rotation of the drill pipe at the earths surface.

A rock bit or roller-cone bit, a common type of bit in use, is normallycomposed of a shank member, which threadedly connects to the lower endof the string of drill pipe, having two or three leg members whichextend downwardly from the shank. The lower end of each leg member formsa shaft which extends inwardly and downwardly toward the axis of thebit. Roller-cone cutters are rotatably supported on the shaft of eachleg. As the drill pipe is rotated, the bit also rotates and as the bitrotates, each individual cone cutter rotates about the shaft of the legmember on which it is supported. The rotates about the bottom of thehole. The cutting surfaces or teeth of each cone contact the bottom ofthe hole to dislodge the formation material by twisting, tearing,gouging, chipping and crushing action.

The condition of the cutter teeth on the rotary rock bit is important inthe drilling of deep wells and it is especially important to know whenthe teeth are worn to the extent that inefficient drilling results fromfurther use of the rock bit.

Therefore, a primary object of the present invention is to provide a newand improved rotary rock bit which will give indications at the earthssurface when the teeth of the bit have become so worn that further usethereof would result in ineflicient drilling operations.

In accordance with the teachings of the present invention, the welldrill bit comprises a shank attachable to the lower end of a drillstring; a leg thereon having a shaft integral with and extendinginwardly of said leg; a cone containing cutter teeth rotatively mountedon said shaft; a first chamber adjacent said bit capable offiuidlycommunicating the interior and exterior of said drill string; a plugremovably arranged in said first chamber; a second chamber intersectingsaid first chamber; a wear probe means arranged in said second chamberand extending therefrom to engage teeth of said cone; means releasablycoupling said indicator plug and said probe means to permit fluidpressure within said drill string to remove said indicator plug uponmovement of said probe means downwardly in response to wear of saidteeth in contact with said probe means whereby an indication of removalof said indicator plug is provided at the surface by a drop in drillingfluid circulating pressure. The probe means is preferably arranged so asto engage the heel teeth of the cone containing the most webbed teeth.Although fluid pressure exerted on the probe means from within the drillstring should provide adequate downward force to maintain the probemeans in contact with the teeth of the cone, where additional downwardforce is desired or necessary, a compression spring located above theprobe means may be used to apply such additional force to the probemeans.

The above objectand other objects and advantages of the invention willbe apparent from a more detailed description thereof when taken with thedrawings wherein:

FIG. 1 is a front view partly in section illustrating the drill bitapparatus in accordance with the invention prior to excessive wear ofthe teeth of the bit; and

FIG. 2 is a side view of a portion of the drill bit apparatus shown inFIG. 1.

Referring to the drawings in greater detail, in FIG. 1 is shown a bitshank 10 attachable to the lower end of a string of drill pipe (notshown) from which a leg portion 11 downwardly extends. Two or three suchleg portions are usually provided; however, for purposes of illustratingthis invention, only one leg portion and associated elements will bedescribed. A spindle or shaft 12 formed integral with leg member 11extends downwardly and inwardly toward the axis of the bit. A rollercone 13 provided with cutter teeth 14 including heel teeth 15 isrotatably mounted on spindle 12 by means of antifriction bearings 16 and17. Shank 10 has an interior chamber 18 in fluid communication with theinterior of the drill pipe at its upper end (not shown) and a passageway19 at its lower end to provide a conduit for the drilling fluid throughthe shank of the drill bit to the cutters thereof. A cylindrical chamberor hole 20 extending laterally from the exterior of shank 10 to theinterior chamber 18 is formed in shank 10. An indicator plug 21 providedwith seals 22 at one end and a retainer pin 23 at the other end thereofis arranged in chamber 20.

Another chamber 24 formed in shank 10 extends downwardly from abovechamber 20 to the interior of leg 11 adjacent the row of heel teeth 15and intersects chamber 20. As also shown in FIG. 2, a wear probe 25,provided with seals 26 and a wear probe pad 27v and formed of enlargedand narrowed portions 28 and 29, respectively, is arranged in chamber24. A compression spring 30 is arranged in chamber 24 above the upperend of wear probe 25. A release slot 31 having a narrowed portion 32 andan enlarged portion 33 is formed in wear probe 25 adjacent intersectionof chambers 20 and 24. Retainer pin 23 extends through release slot 31,as shown in FIGS. 1 and 2.

Wear probe 25 is arranged to engage the heel teeth of one of the cuttercones, preferably of the cutter cone, if any, which contains the mostwebbed heel teeth. The webbing designated 35 in FIG. 2 inhibitsexcessive gauge wear, breaks up the bottom of the hole adjacent theborehole wall and removes rock teeth at the junction of the boreholewall and the bottom of the borehole. Such webbing may interconnect twoteeth, three teeth, or four teeth. It is not necessary for the row ofheel teeth to contain webbing, for the wear probe would be madesufficiently wide so that its lower surface would always be in contactwith at least two teeth.

Attention is now directed to operation of the drill bit. With theelements of the drill bit in their positions shown in FIGS. 1 and 2,drilling fluid is circulated down the drill string through chamber 18and passageway 19 and around the cutter cones 13 and upwardly past shank10 and through the annulus between the drill pipe and the borehole wallto the earths surface. While drilling fluid is circulated in thismanner, the drill pipe and shank 10 are rotated, which causes cone 13 torotate on spindle 12. Wear probe 25 is urged downwardly by pressure ofthe circulating drilling fluid acting on the upper surface of theenlarged diameter portion seals 26 of wear probe 25 (and also, ifincluded, by compression spring 30) into engagement with the row of heelteeth 15. Indicator plug 21 is retained in chamber 20 by means ofretainer pin 23 which is held in the narrow portion 32 of release slot31. As the teeth of cutter 13 wear down, wear probe 25, continuallyurged into engagement with teeth 15, moves downwardly. Fluid pressurefrom the circulating drilling fluid acts against the indicator plug andwhen wear probe 25 moves downwardly a suflicient amount to positionenlarged portion 33 of release slot 31 adjacent retainer pin 23,indicator plug 21 is released and is removed from chamber by thecirculating drilling fluid. A distinct drop in drilling fluidcirculating pressure is then indicated at the surface, which shows thatthe heel teeth on cone 13 are worn to such an extent that inefficientdrilling will result from further use of the bit.

The invention is not to be restricted to the specific details set forthas various modifications thereof may be made without departing from thescope of this invention. For example, a short sub member mounted on thebit could be provided with the chamber and indicator plug instead of theshank of the bit as shown and described above. In such modification, thewear probe would extend through a hole bored in the bit.

Having fully described the objects, advantages, apparatus and mode ofoperation of my invention, I claim:

1. A drill bit comprising:

a shank member;

a leg extending therefrom provided with a shaft ex tending downwardlyand inwardly of said leg;

a cone containing rows of cutter teeth rotatively mounted on said shaft;

a first chamber in said shank extending from the exterior to theinterior thereof in fluid communication with said circulating drillingfluid;

an indicator plug removably-arranged in said first chamber;

a second chamber in said shank intersecting said first chamber andcontaining probe means, the lower end of which engages said cone teeth;and

means releasably coupling said indicator plug and said probe meansadapted to release said indicator plug to permit removal of saidindicator plug by drilling fluid pressure within said shank upondownward movement of said probe means in response to wear of said coneteeth whereby an indication of removal of said indicator plug isprovided at the surface by a drop in drilling fluid circulatingpressure.

2. A drill bit as recited in claim 1 including a compression springarranged in said second chamber above said probe means adapted to urgesaid probe means downwardly into engagement with said cone teeth.

3. A drill bit as recited in claim 1 in which said means coupling saidindicator plug and said probe means includes a release slot in saidprobe means having a narrow portion and an enlarged portion andincluding a retainer pin arranged on said indicator plug, said narrowslot portion retaining said pin and said enlarged slot portionpermitting release of said pin to permit drilling fluid pressure toremove said indicator plug from said first chamber.

4. In rotary drilling apparatus employing a drill string through whichdrilling fluid is circulated during drilling operations, the improvementcomprising:

means attachable to the lower end of said drill string having meanscontaining cutter teeth rotatively mounted thereon;

a first chamber formed in said means attachable to the lower end of saiddrill string capable of fluidly communicating the interior and exteriorof said drill string;

an indicator plug removably arranged in said first chamber;

a second chamber formed in said means attachable to the lower end ofsaid drill string intersecting said first chamber and containing probemeans the lower end of which engages said cutter teeth; and

means releasably coupling said indicator plug and said probe meansadapted to release said indicator plug to permit removal of saidindicator plug by drilling fluid circulating pressure upon downwardmovement of said probe means in response to Wear of said cutter teethwhereby an indication of removal of said indicator plug is provided atthe surface by a drop in drilling fluid circulating pressure.

5. Apparatus as recited in claim 4 including spring means arranged insaid second chamber above said probe means adapted to urge said probemeans downwardly into engagement with said cutter teeth.

6. Apparatus as recited in claim 4 in which said means coupling saidindicator plug and said probe means includes a release slot in saidprobe means having a narrow portion and an enlarged portion andincluding a retainer pin arranged on said indicator plug, said narrowslot portion retaining said pin and said enlarged slot portionpermitting release of said pin to permit drilling fluid pressure toremove said indicator plug from said first chamber.

References Cited UNITED STATES PATENTS 2,549,278 4/1951 Yancey -392,658,724 11/1953 Arps 175-39 X 3,058,532 10/1962 Alder 17539 CHARLES E.OCONNELL, Primary Examiner.

I. A. CALVERT, Assistant Examiner.

4. IN ROTARY DRILLING APPARATUS EMPLOYING A DRILL STRING THROUGH WHICHDRILLING FLUID IS CIRCUATED DURING DRILLING OPERATIONS, THE IMPROVEMENTCOMPRISING: MEANS ATTACHABLE TO THE LOWER END OF SAID DRILL STRINGHAVING MEANS CONTAINING CUTTER TEETH ROTATIVELY MOUNTED THEREON; A FIRSTCHAMBER FORMED IN SAID MEANS ATTACHABLE TO THE LOWER END OF SAID DRILLSTRING CAPABLE OF FLUIDLY COMMUNICATING THE INTERIOR AND EXTERIOR OFSAID DRILL STRING; AN INDICATOR PLUG REMOVABLY ARRANGED IN SAID FIRSTCHAMBER; A SECOND CHAMBER FORMED IN SAID MEANS ATTACHABLE TO THE LOWEREND OF SAID DRILL STRING INTERSECTING SAID FIRST CHAMBER AND CONTAININGPROBE MEANS AND LOWER END OF WHICH ENGAGES SAID CUTTER TEETH; AND MEANSRELEASABLY COUPLING SAID INDICATOR PLUG AND SAID PROBE MEANS ADAPTED TORELEASE SAID INDICATOR PLUG TO PERMIT REMOVAL OF SAID INDICATOR PLUG BYDRILLING FLUID CIRCULATING PRESSURE UPON DOWNWARD MOVEMENT OF SAID PROBEMEANS IN RESPONSE TO WEAR OF SAID CUTTER TEETH WHEREBY AN INDICATION OFREMOVAL OF SAID INDICATOR PLUG IS PROVIDED AT THE SURFACE BY A DROP INDRILLING FLUID CIRCULATING PRESSURE.